Mussel spat ropes provide passage for banded kokopu (Galaxias fasciatus) in laboratory trials

Abstract

The use of mussel spat ropes to enable the passage of banded kokopu (Galaxias fasciatus) past perched culverts was tested under laboratory conditions. A 0.5 m high simulated perched culvert was fitted with one of two UV stabilised polypropylene rope types: “Russet Loop” and “Super Xmas Tree”. Four randomised replicate trials using each rope type were conducted to test their respective abilities to provide passage for “fresh-run” banded kokopu whitebait (migrating post-larval juveniles). There was no statistical difference in performance between the two rope types, with both performing equally well over each 3 h trial. A high proportion of fish used the ropes to successfully negotiate the structure (mean >85% individuals per trial irrespective of rope type). The high rate of successful passage over a short time period suggests that these ropes may be an effective, affordable and potentially easy retrofit to perched culverts, particularly for native species with similar climbing capabilities to banded kokopu.